test: cover reset after network override

internal/composego/loader_test.go

@@ -0,0 +1,68 @@
+/*
+   Copyright 2026 Docker Compose CLI authors
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package composego
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	composeloader "github.com/compose-spec/compose-go/v2/loader"
+	composetypes "github.com/compose-spec/compose-go/v2/types"
+	"gotest.tools/v3/assert"
+)
+
+func TestExtendsResetDoesNotLeakOverriddenNetworkAliases(t *testing.T) {
+	tmpDir := t.TempDir()
+	composeFile := filepath.Join(tmpDir, "compose.yaml")
+	composeContent := `
+services:
+  service_a:
+    image: php:latest
+    networks:
+      default:
+        aliases:
+          - oss-a.xyz
+  service_b:
+    extends:
+      service: service_a
+    networks: !override
+      default:
+        aliases:
+          - oss-b.xyz
+  service_c:
+    extends:
+      service: service_b
+    networks: !reset []
+`
+	err := os.WriteFile(composeFile, []byte(composeContent), 0o644)
+	assert.NilError(t, err)
+
+	project, err := composeloader.LoadWithContext(t.Context(), composetypes.ConfigDetails{
+		WorkingDir:  tmpDir,
+		Environment: composetypes.Mapping{},
+		ConfigFiles: []composetypes.ConfigFile{{Filename: composeFile}},
+	}, func(options *composeloader.Options) {
+		options.SetProjectName("compose-13348", true)
+	})
+	assert.NilError(t, err)
+
+	// Regression test for docker/compose#13348: the chained reset must not mutate
+	// service_b and reintroduce service_a's aliases after service_b used !override.
+	serviceB := project.Services["service_b"]
+	assert.DeepEqual(t, []string{"oss-b.xyz"}, serviceB.Networks["default"].Aliases)
+}